Finally I tried to make some photographs near the opening, which is something I rarely do because of the difficulty in accurately portraying the two mixing types of light. For reasons I don't claim to understand, the balance was right in this case.
I think the result is more "mysterious" and less just plain otherworldly. The square format was a product of both how I was seeing the subject and this being stitched from two images for a pinch more detail.
Happy Alaska Day everyone!